Self-levelling vehicle lamps

ABSTRACT

A self-levelling vehicle light system in which a control from the vehicle suspension provides a signal in accordance with changes in attitude of the vehicle relative to the road. A lamp support is tiltable about a horizontal pivotal axis in response to the signal, a resilient connection being provided both between the signal and the lamp support and the lamp support and a fixed mounting and a damper being provided for damping sudden movements of the lamp support.

United States Patent [451 Jan. 18,1972

Martin 5 SELILLEVELLING VEHICLE LAMPS 3,316,397 4/1967 Yssel ..240/7.l

3,402,287 9/1968 'Hindman [72] Inventor: Frederick R. P. Martin, BromleyKent, 3 336 470 3/19 7 Sombardier England 2,984,737 5/1961 Marcellus..240/7.1

[73] Assignee: na -3 3:3 Development Limited Lon- PrimaryExaminer-Samuel S. Matthews Assistant Examiner-Russell B. Adams, Jr.[22] Filed: May 8, 1969 Attorney-Stevens, Davis, Miller & Mosher 21Appl. No.: 822,978 [57] ABSTRACT A self-levelling vehicle light systemin which a control from [30] Foreign Application Priority Data 7 thevehicle suspension provides a signal in accordance with May 13, 1968Great Britain ..22601/68 changes in attitude of the vehicle relative tothe road. A lamp Feb. 21, 1969 Great Britain ..9618/69 support istiltable about a horizontal pivotal axis in response to I the signal, aresilient connection being provided both between [52] 11.5. ..240/7.1 L]the signal and the lamp support and the lamp support and a [51] Int. Cl..B60g 1/10 fixed mounting and a damper being provided for damping sud-[58] Field of Search ..240/7. 1, 7.1 U d n v m n s f the lamp support.

[56] References Cited ismls mntris za UNITED STATES PATENTS 3,370,1622/1968 Henry-Biabaud" d) /2 4 i L6 r I \l T i "r L l i Y 6 i l 7 9 l i"5 f g l 2 II I 7 I PA PATENTED JAIN 81912 sum 1 OF 5 PATENTEnJmmmz3.636.343

SHEET 4 [IF 5 PATENTEU JAN 1 8 I9 2 SHEET 5 0F 5 SELF-LEVELLING VEHICLELAMPS This invention relates to self-levelling vehicle lamps and moreespecially to self-levelling vehicle lamp systems which include meansfor adjusting the angle of projection in azimuth of the vehicle lamp totake into account changesin attitude of the vehicle in which it ismounted, as by reason of changes in static loading of the vehicle or thedynamic forces due to acceleration and deceleration.

Accordingto the invention there is provided a self-levelling vehiclelamp system comprising means for pivoting a lamp support about asubstantially horizontal axis, means for damping pivoted movement of thelamp support, and means forapplying a correcting bias via a resilientlinkage to tilt the lamp support as a result of a control signal derivedfrom a change in vehicle attitude. Conveniently the signal may bederived from the vehicle suspension as, for instance, from displacementof the rear suspension. Thus conveniently the signal may be derived frompivotal movements of a torque arm connecting the rear wheel suspensionto the vehicle body so that loading of the rear of the vehicle whichcauses the vehicle attitude to be inclined downwardly to the rear andwhich would cause a fixed headlamp to project an upwardly directed beam,can cause the lamp to be tilted downwardly about a horizontal axis so asto maintain an optimum angle of projection.

Preferably the resilient linkage comprises a pair of interconnectedsprings arranged in series, one being connected to a fixed mounting andthe other being connected to receive the control signal, the lampsupport being controllable by movements of the point of interconnection.

While under most circumstances it is the rear suspension of a passengercar which has the greatest effect on the attitude of the vehicle thefront suspension also does get displaced due to static loadingconditions, and even more so due to dynamic variation as a result ofacceleration or deceleration. Accordingly it is preferred that thesignal to the lamp should be derived from both the front and rearvehicle suspensions so that the signal passed to the lamp is a resultantof the different signals obtained from the front and rear suspensions.

Conveniently the signal may be taken from the rear suspension to thelamp by a cable or linkage additionally displaceable by movement of thefront suspension. In the particularly described embodiment the cablepasses from the rear suspension to the lamp via a guide mounted on thefront suspension whereby the cable is slackened or tightened by up anddown movements of the front wheel relative to the vehicle body. Thecable may be an encased cable which is bent in an arc to pass throughthe guide so that curvature of the cable is varied in accordance withthe deflectionof the front suspension to cause consequent displacementof the inner force-transmitting cable.

In one embodiment there may be provided a summation linkage provided forgiving a single output signal for controlling the lamp support inresponse to two input signals derived respectively from the front andrear vehicle suspensions. Preferably the summation linkage comprises anoutput lever and a pair of spaced pivotal connections to the outputlever, each of the pivotal connections being movable in response to aseparate one of the input signals and an output signal connection beingsecured to the pivotal lever whereby the position of the outputconnection is responsive to the position of both the pivotalconnections. Suitably one of the pivotal connections may be directlymovable in response to one input signal and the other is movable via abellcrank, one arm of which is pivotally connected to the output leverat the other pivotal connection.

When a vehicle is, for example, loaded at the rear as due to heavyloading of the trunk or due to a sharp acceleration, a fixed headlightwould tend to be directed upwardly at too high an angle relative to thehorizontal with a resultant tendency to dazzle oncoming drivers. Withthe latter arrangement signals from the vehicle suspension would betransmitted to the summation linkage from which an output signal canbederived as a result of the movements of both the front and rearsuspensions, this output signal being usedto control the angle ofprojection in azimuth of the vehicle headlamp. By a proper proportioningof the summation linkage equal deflections of the front and rearsuspension, which would not change the attitude of the vehicle on theroad and thus the angle or projection of a fixed lamp, are cancelled outso that no output would be derived from the linkage, whereas when one ofthe front and rear suspensions is deflected more than the other anoutput signal is produced which produces the appropriate correction inthe angle of projection of the vehicle headlamp.

Preferably the cable is held taut by a spring and is connected via theresilient linkage to the pivotal lamp support. Suitably the cable may beconnected to a 1 pivoted control lever, a resilient connection beingprovided between the lever and the lamp support. By appropriatelypositioning along the lever the points of connection between the leverand the cable and the lever and the lamp support the tilting movementsof the lamp support will be in the appropriate ratio relative to themovements of the cable caused by deflections of the vehicle suspension.

Preferably the lamp support is pivoted about a central horizontal axisand is connected via a spring with the lever. The provision of a centralhorizontal axis is important if the lamp to be carried by the lampsupport is to be exposed to the airstream since the pressure of aircontacting the front of the lamp would then be balanced above and belowthe horizontal support. Unwanted deflection of the lamp will not then becaused as a result of variation in vehicle speed causing a consequentialvariation in the pressure of air contacting the front of the lamp.

In a particularly simple embodiment, as described later, tension springsare connected to the top and bottom of the lamp support to exert forcesbiasing the lamp in opposite directions about the horizontal pivot, onespring being connected to the lever and the other to a fixed mounting.The fixed'mounting and/or the spring connection tothe lever arepreferably adjustable to permit alteration of the spring tension tofacilitate adjustment of the position of the lamp support.

The means for damping pivotal movement of the lamp support may comprisea piston reciprocatable in a cylinder containing liquid in aconventional manner. The provision of the damping means is of importancesince the damping means prevents substantial movement of the lampsupport as a result of quick deflections of the vehicle wheels, as whengoing over bumps, but allows proper response to less transientdeflections of the suspension, as during acceleration or deceleration ofthe vehicle, when the vehicle is going up or down slopes, or resultingfrom changes in static loading of the vehicle as when additionalpassengers or luggage is loaded thereinto.

The invention will be furtherdescribed, merely by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a side elevational diagrammatic view partly in sectionrof alamp mounting for a lamp system embodying the invention;

FIG. 2 is a diagrammatic plan view partly in section of the lamp housingof FIG. 1;

FIG. 3 is a diagrammatic illustration showing means for deriving asignal'from the rear suspension of a vehicle;

FIG. 4 is a diagrammatic view looking forward beneath the fender of avehicle illustrating how a signal may be derived from the .frontsuspension of a vehicle;

FIG. 5 is adetailed view of an alternative form of part of theconstruction shown in FIG. 4; and

FIG. 6 is a diagrammatic view of a summation linkage which may be usedto add signals obtained from the front and rear suspensions.

Referring to the drawings, and in particular FIGS. 1 and 2, there isshown a lamp nacelle 1 adapted to be fixedly secured as a front lamphousing of a vehicle. An annular plate 2 surrounds the front rim of thenacelle'l and supports, by means of a horizontalaxis'pivot 3, a lampsupport 4. A lamp 6 is carried by the support 4 and is accuratelypositionable therein by means of conventional screw adjusters 5. Theheight of the axis of pivot 3 is such as to permit the lamp 6 to pivotabout a horizontal axis substantially half way up the height of thelamp.

An arm 7 extends rearwardly of the lamp support and is connected by apivot 8 to a piston rod 9 carrying a piston 10 for reciprocation in acylinder 11 of a fluid-filled damper, the cylinder 1 I being secured tothe rear wall of the nacelle 1. The damper I0, 11 thus acts to damptilting movements of the lamp support 4 about the horizontal axis ofpivot 3.

A tension spring 12 is secured at one end the lamp support 4 by amounting 13 and is secured at the other end to a mounting 14 fixed tothe nacelle 1 via a spring tension adjuster 15. A similar springarrangement 16, shown in FIG. 2 as being formed of two tension springsin-parallel, is secured via supports 17 to the bottom of lamp support4,the other ends of the springs 16 being secured by a tension adjuster 18to a control lever 19. The control lever 19, as shown in FIG. 2, ispivoted at one end 22 to the inside of the nacelle and projects at theother end through a slot 23 extending horizontally of the nacelle so asto provide a guide and mounting for the lever permitting it to pivot ina horizontal plane. Extending rearwardly from the lever 19 is the core20 of an encased cable 21, movements of the core 20 providing a signalfor controlling the angle of tilt of the lamp support 4 about thehorizontal axis 3. A strong tension spring 24 is secured at one end 25to the inside surface of the nacelle and at the other end to the lever19 to maintain the core 20 of the control cable tensioned.

Referring to FIG. 3 the rear end of the core 20 encased in wall 21, isshown secured by an adjuster 27 to a, lever arm 26 secured to the torqueann mounting 28 of the rear suspension of the vehicle. With thisarrangement upon changing in loading of the vehicle the torque arm 28will rotate about its mounting with consequential movement of the leverarm 26 causing displacement of the core 20 of the control cable 21.

FIG. 4 is a diagrammatic view showing how the cable 21 passes forwardlythrough an eye 31 in a guide 32 before reaching the position where thecore is connected to the control lever 19. For convenience in thisarrangement the cable 21 is shown connected to the lever 19 interiorlyof the nacelle 1 although it is preferred to have the cable connected tothe lever 19 exteriorly of the nacelle as shown in FIGS. 1 and 2. Theguide 32 is secured to the upper suspension arm 29 which is pivotalabout a support pivot 30 in response to up and down movements of thevehicle front wheel assembly relative to the vehicle body. Pivotalmovements of the arm 29 about pivot 30 will cause consequential movementof the eye 31 of the guide so as to change the curvature of the cablewhere it passes through the guide. This movement is sufficient to adjustthe cable to provide a signal to the lamp responsive to movements of thetop suspension arm 29 of the front vehicle suspension.

FIG. shows an alternative arrangement where instead of having a guidebracket 32 a guide bracket 32 is shown secured to a top suspension arm29. The cable passes around a pulley 33 carried by the guide bracket32'.

Although described in relation to an encased cable 21 it will beappreciated that the casing for the control wire is not essential, andalso that the signals from the rear and front suspensions can be derivedin alternative ways provided that the proper relationship is retainedbetween the front and rear suspension deflections to provide a properdifference signal to the lamp. Thus it should be appreciated that if thefront and rear suspensions are deflected to an equal extent there willbe no change in attitude of the car relative to the road so thatconsequently the movements of the cable caused by the two deflectionsshould cancel out so that no signal is passed to the lamp to change itsangle of projection.

While FIG. I shows the top tension spring 12 as being connected betweenthe fixed mounting and the lamp support 4 and the bottom spring 16 beingconnected between the lamp support and the control lever 19 the springsmay be reversed provided that suitable changes are made so that thedeflections of the vehicle suspension cause an appropriate directionalsignal to be applied to control the angle of projection of the lamp.

As shown in FIG. 2 the points of connection of the cable core 20 and thespring adjuster 18 to the lever 19 are so spaced from the pivot 22 thatthe rearward end of the tension spring 16 will be moved through abouthalf the movement of the cable core 20. This movement is further reducedby about a half during transmission to the lamp support 4 due to thecontraction or expansion of the springs 16 and 12 as a result of themovement applied to them by movement of the control lever 19.

During normal operation of the system, changes in loading of the vehiclewill cause a change in attitude of the front suspension arm and/or reartorque arm so that an appropriate signal causes a proportional movementof the lever 19. Movement of the lever 19 is transmitted to the lampsupport 4 so as to cause an adjustment of the lamp 6 to ensure that itretains its proper angle of projection in azimuth despite changes inattitude of the vehicle. Changes in attitude of the vehicle occurringduring acceleration or deceleration or due to a change in slope of theroad over which the vehicle is passing will cause corresponding changesin angle of projection of the lamp due to the lamp support 4 being movedabout its horizontal pivot as a result of deflection of the front andrear suspensions. The effect of the damper 10, 11 is to delay immediateresponse of the lamp mounting 4 so that changes in angle of projectionof the lamp as a result of short sharp impulses from the suspensionsystem, as when a wheel passes over a bump in the road, are negligible.Thus when the vehicle is travelling over a rough surface at high speedits wheels may bounce violently and yet, because these movements arevery quick, the damper prevents immediate registration of such quickmovements on the angle of projection of the lamp, the quick movementsbeing taken up by rapid deflections of the spring 16.

While combined tension springs 12 and 16 have been shown in theillustrated embodiment it will be appreciated that other spring meansmay be utilized for providing the resilient connection between the inputfor the transmission signal and the lamp itself so as to enable thedamper to function properly to prevent too rapid a response of the lampto transient suspension movements.

The control operated by the front suspension, as indicated above, worksin reverse to the control provided at the rear of the car. If the rearend of a car goes down the rear wheel signal must cause dipping of thelights but if the front end goes down it must raise the lights, and viceversa, if proper angle of projection of the lamps is to be obtained.Thus in the case of a heavy load being applied to the trunk of a car therear signal will dip the lights in proportion to the trunk load, butbecause, the front lifts as well to a slight extent this will cause asmall additional signal to be added to cause additional dipping.Similarly for example, a car going up a steep hill will-not only go downat the rear but will lift at the front, and the two signals willcompensate for this.

While, in general, any convenient means may be used to obtain a controlsignal for the lamps in response to initial signals obtained from boththe front and rear suspensions of the vehicle, a particularly convenientform of summation linkage is illustrated in FIG. 6 for converting theinput signals from the front and rear vehicle suspensions into a singleoutput signal which may be used to control the angle of projection ofthe vehicle lamp.

Referring to FIG. 6 there is illustrated a flat box 51 into which is leda first input cable 52 encased by a casing 53. The second input to thebox 51 comprises a cable 54 secured for movement with the lowersuspension arm 66 of the front suspension of a vehicle. The cable 52 isconnected for movement in response to the movement of the rear vehiclesuspension.

The cable 52 is connected by an adjustable screw connector 56 to a pivotsupport 57 provided at 58 with a pivotal connection to an output lever59. The other end of the output lever 59 is provided with a pivotalconnection 61 to one am of a bellcrank lever 62 which is pivoted at 63to the box 51. The other arm of the bellcrank lever 62 is connected at64 to the input cable 54. An output cable 55 is connected via an outputconnection 60 to the output lever 59. As shown a tension spring 65 isprovided to assist in maintaining the cable 54 taut.

When the summation linkage is mounted in a vehicle having aself-levelling headlight system of the kind illustrated and describedabove, the cable 55 is connected to a self-levelling vehicle lampmounting and is maintained in tension. Accordingly the tension in thecable 55 helps to maintain cable 54 tensioned and also applies a tensionvia the lever 59 to the cable 52 leading to the rear vehicle suspension.With the arrangement shown an upward deflection of the rear wheels ofthe vehicle due, for example, to heavy loading of the trunk of thevehicle, causes cable 52 to be pulled rearwardly with consequentrearward movement of the pivotal connection 58 and a smaller rearwardmovement of the output connection 60 with consequent movement of theoutput cable 55 to cause tilting of the headlamp of the vehicle tocounteract the downward tilting of the rear of the vehicle. Similarly areduction in deflection of the front vehicle suspension will causedownward movement of the cable 54 with a consequent rearward movement ofthe cable 55 to cause a downward dipping of the vehicle headlamps.Opposite movement of the output cable 55 with upward tilting of thevehicle headlamp will be caused if the loading at the rear of thevehicle is reduced or the loading at the front of the vehicle isincreased. Preferably the position of the output connection 60 along theoutput lever 59 is adjustable so that the proportional efiect of thefront and rear suspensions may be adjusted. Thus if the outputconnection 60 is moved nearer to the pivotal connection 58 from theposition shown on the drawing this would have the effect of increasingthe output movement of the cable 55 and thus displacement of the lamp inresponse to a given deflection of the rear suspension, and wouldsimilarly have the effect of reducing the movement of the output cable55 in response to deflection of the first suspension.

lclaim:

l. in an automotive vehicle having a resiliently displaceablesuspension, a self-levelling lamp system comprising a lamp support,means mounting said lamp support for pivotal move ment, a resilientforce transmission linkage connected to said lamp support,signal-providing means carried by said vehicle suspension to provide amechanical signal having an amplitude responsive to displacements of thevehicle relative to a road surface and a mechanical signal-transmittingmeans con nected between said signal-providing means and said linkage,said resilient linkage applying a correcting bias to tilt the lampsupport responsive to changes in said mechanical signal upon changes invehicle attitude as measured by aid signal-providing means, wherein thesignal-transmitting means includes a summation linkage having a singleoutput signal member connected to said linkage and first and secondinput members connected to the signal-providing means at the front andrear vehicle suspension respectively, said summation linkagecomprising afixed housing, an output lever having said output signal member securedthereto, and a bellcrank pivoted to said housing and having one armpivotally supporting one end of the output lever, the other end of saidoutput lever being pivoted to the second input signal member, saidsecond input signal member being carried by said housing for movementsubstantially at right angles to said output member and said first inputsignal member being secured to the other arm of said bellcrank wherebythe position of the output signal member is responsive to the positionof both the input signal members.

2. in an automotive vehicle having a resiliently displaceablesuspension, a self-levelling lamp system comprising a lamp support,means mounting said lamp support for pivotal movement, a resilient forcetransmission linkage connected to said lamp support, signal-providingmeans carried by said vehicle suspension to provide a mechanical signalhaving an amplitude responsive to displacements of the vehicle relativeto a road surface and a mechanical signal-transmitting means connectedbetween said signal-providing means and said linkage, said resilientlinkage applying a correcting bias to tilt the lamp support responsiveto changes in said mechanical signal upon changes in vehicle attitude asmeasured by said signal-providing means, and further comprising a fixedmounting secured to said vehicle and wherein the resilient linkagecomprises a pair of interconnected spring means arranged in series withone spring means being connected to an tensioned between said fixedmounting and the interconnection with the other spring means, said otherspring means being connected and tensioned between said interconnectionand the signal-transmitting means, said lamp support being controlled inaccordance with movements of said interconnection.

3. in an automotive vehicle having a resiliently-displaceablesuspension, a self-levelling lamp system comprising a lamp support,means mounting said lamp support for pivotal movement, a resilient forcetransmission linkage connected to said lamp support, signal-providingmeans carried by said vehicle suspension to provide a mechanical signalhaving an amplitude responsive to displacements of the vehicle relativeto a road surface and a mechanical signal-transmitting means connectedbetween said signal-providing means and said linkage, said resilientlinkage applying a correcting bias to tilt the lamp support responsiveto changes in said mechanical signal upon changes in vehicle attitude asmeasured by said signal-providing means, wherein the signal-transmittingmeans comprises a pivoted control output lever pivotally movable inresponse to the transmitting signal, said lamp system including a fixedspring mounting and the resilient linkage comprising tension springsconnected to the top and bottom of the lamp support to exert forcesbiasing the lamp support in opposite directions, one spring beingconnected to the control lever and the other to said fixed springmounting.

4. A lamp system according to claim 1, wherein the position ofsecurement of the output signal member to the output lever is adjustablelengthwise of the output lever.

5. A lamp system according to claim 2, wherein the lamp support itselfprovides said interconnection, both said spring means being directlyconnected to said lamp support.

6. A lamp system according to claim 3, including adjustable meansconnecting the springs respectively to said control lever and said fixedspring mounting whereby the spring tensions are adjustable.

7. In a vehicle having road wheels, a body and a resilientlydisplaceable suspension supporting the body on the road wheels, aself-levelling lamp system comprising a lamp, means mounting said lampfor pivotal movement about a substantially horizontal axis extendingtransversely of the lamp at midheight thereof, means for damping pivotalmovement of the lamp about said axis, signal-providing means carried bysaid vehicle suspension to provide a mechanical signal having anamplitude responsive to the displacement of the vehicle body relative tothe road wheels, a mechanical signal-transmitting means connectedbetween said signal-providing means and a signal output member, and aresilient linkage connected to said output member for applying acorrecting bias to tilt the lamp support about said axis responsive tochanges in said mechanical signal upon changes in vehicle attitude asmeasured by said signal-providing means, said resilient linkagecomprising a fixed support, a movable member, a first spring tensionedbetween said fixed support and said movable member, and a second springtensioned between said movable member and said output member, saidmovable member being connected with said lamp whereby said lamp ismovable about said axis in accordance with movements of said movablemember.

8. A lamp system according to claim 7, wherein said lamp is carried bysaid movable member, said movable member itself being pivotally mountedfor tilting movement about said horizontal axis.

1. In an automotive vehicle having a resiliently displaceablesuspension, a self-levelling lamp system comprising a lamp support,means mounting said lamp support for pivotal movement, a resilient forcetransmission linkage connected to said lamp support, signal-providingmeans carried by said vehicle suspension to provide a mechanical signalhaving an amplitude responsive to displacements of the vehicle relativeto a road surface and a mechanical signal-transmitting means connectedbetween said signal-providing means and said linkage, said resilientlinkage applying a correcting bias to tilt the lamp support responsiveto changes in said mechanical signal upon changes in vehicle attitude asmeasured by aid signal-providing means, wherein the signal-transmittingmeans includes a summation linkage having a single output signal memberconnected to said linkage and first and second input members connectedto the signal-providing means at the front and rear vehicle suspensionrespectively, said summation linkage comprising a fixed housing, anoutput lever having said output signal member secured thereto, and abellcrank pivoted to said housing and having one arm pivotallysupporting one end of the output lever, the other end of said outputlever being pivoted to the second input signal member, said second inputsignal member being carried by said housing for movement substantiallyat right angles to said output member and said first input signal memberbeing secured to the other arm of said bellcrank whereby the position ofthe output signal member is responsive to the position of both the inputsignal members.
 2. In an automotive vehicle having a resilientlydisplaceable suspension, a self-levelling lamp system comprising a lampsupport, means mounting said lamp support for pivotal movement, aresilient force transmission linkage connected to said lamp support,signal-providing means carried by said vehicle suspension to provide amechanical signal having an amplitude responsive to displacements of thevehicle relative to a road surface and a mechanical signal-transmittingmeans connected between said signal-providing means and said linkage,said resilient linkage applying a correcting bias to tilt the lampsupport responsive to changes in said mechanical signal upon changes invehicle attitude as measured by said signal-providing means, and furthercomprising a fixed mounting secured to said vehicle and wherein theresilient linkage comprises a pair of interconnected spring meansarranged in series with one spring means being connected to an tensionedbetween said fixed mounting and the interconnection with the otherspring means, said other spring means being connected and tensionedbetween said interconnection and the signal-transmitting means, saidlamp support being controlled in accordance with movements of saidinterconnection.
 3. In an automotive vehicle having a resilientlydisplaceable suspension, a self-levelling lamp system comprising a lampsupport, means mounting said lamp support for pivotal movement, aresilient force transmission linkage connected to said lamp support,signal-providing means carried by said vehicle suspension to provide amechanical signal having an amplitude responsive to displacements of thevehicle relative to a road surface and a mechanical signal-transmittingmeans connected between said signal-providing means and said linkage,said resilient linkage applying a correcting bias to tilt the lampsupport responsive to changes in said mechanical signal upon changes invehicle attitude as measured by said signal-providing means, wherein thesignal-transmitting means comprises a pivoted control output leverpivotally movable in response to the transmitting signal, said lampsystem including a fixed sprIng mounting and the resilient linkagecomprising tension springs connected to the top and bottom of the lampsupport to exert forces biasing the lamp support in opposite directions,one spring being connected to the control lever and the other to saidfixed spring mounting.
 4. A lamp system according to claim 1, whereinthe position of securement of the output signal member to the outputlever is adjustable lengthwise of the output lever.
 5. A lamp systemaccording to claim 2, wherein the lamp support itself provides saidinterconnection, both said spring means being directly connected to saidlamp support.
 6. A lamp system according to claim 3, includingadjustable means connecting the springs respectively to said controllever and said fixed spring mounting whereby the spring tensions areadjustable.
 7. In a vehicle having road wheels, a body and a resilientlydisplaceable suspension supporting the body on the road wheels, aself-levelling lamp system comprising a lamp, means mounting said lampfor pivotal movement about a substantially horizontal axis extendingtransversely of the lamp at midheight thereof, means for damping pivotalmovement of the lamp about said axis, signal-providing means carried bysaid vehicle suspension to provide a mechanical signal having anamplitude responsive to the displacement of the vehicle body relative tothe road wheels, a mechanical signal-transmitting means connectedbetween said signal-providing means and a signal output member, and aresilient linkage connected to said output member for applying acorrecting bias to tilt the lamp support about said axis responsive tochanges in said mechanical signal upon changes in vehicle attitude asmeasured by said signal-providing means, said resilient linkagecomprising a fixed support, a movable member, a first spring tensionedbetween said fixed support and said movable member, and a second springtensioned between said movable member and said output member, saidmovable member being connected with said lamp whereby said lamp ismovable about said axis in accordance with movements of said movablemember.
 8. A lamp system according to claim 7, wherein said lamp iscarried by said movable member, said movable member itself beingpivotally mounted for tilting movement about said horizontal axis.